1. Field of the Invention
The present invention relates to powered valve actuators for remotely-controlled operation of valves and, more particularly, to actuators for handwheel-operated valves.
2. Description of the Prior Art
Fluids under pressure are often stored or transported in a vessel having a valve at its top which is operated by a rotating valve stem to open and close the valve. For vessels which contain fluids which are corrosive, toxic or otherwise dangerous to the operator of the valve, manual operation of the valve is undesirable, since it can be dangerous to the operator if the valve leaks or otherwise permits the escape of the fluid. Accordingly, powered controllers or actuators for such valves have been provided which can be operated from a remote location. In certain types of vessels, such as cargo tanks for railway cars, trucks or the like, the valve stem may be provided with a handwheel for manual rotation. In this case, the actuator must engage the handwheel to effect rotation thereof.
Powered actuators typically include a motor which has a housing and a rotating output shaft which is coupled to the handwheel or operating element for the valve stem to effect rotation thereof. In such powered actuators, it is also necessary to provide a coupling between the motor and the valve so that the torque generated by the motor output shaft does not cause displacement between the motor housing and the valve body. It is also necessary to prevent separation occurring between the valve and the actuator. Therefore, prior actuators have typically provided a means for fixedly securing the actuator to the valve body. This may require the use of a tool, such as a wrench or the like, and also requires the presence of personnel at the valve site to affix the actuator to the valve and to disconnect it when the valve actuation has been completed.
Many vessels are provided with different sizes and types of valves which may have quite different housing and/or handwheel constructions. Thus, the structure for coupling an actuator to one valve may not be suitable for coupling it to a different type of valve.